(function () {
    //based on an Example by @curran
    window.requestAnimFrame = (function () {
        return window.requestAnimationFrame
    })();
    var canvas = document.getElementById("canvas");
    var c = canvas.getContext("2d");

    var numStars = 1500;
    var radius = '0.' + Math.floor(Math.random() * 9) + 1;
    var focalLength = canvas.width * 2;
    var warp = 0;
    var centerX, centerY;

    var stars = [],
        star;
    var i;

    var animate = true;

    initializeStars();

    function executeFrame() {

        if (animate)
            requestAnimFrame(executeFrame);
        moveStars();
        drawStars();
    }

    function initializeStars() {
        centerX = canvas.width / 2;
        centerY = canvas.height / 2;

        stars = [];
        for (i = 0; i < numStars; i++) {
            star = {
                x: Math.random() * canvas.width,
                y: Math.random() * canvas.height,
                z: Math.random() * canvas.width,
                o: '0.' + Math.floor(Math.random() * 99) + 1
            };
            stars.push(star);
        }
    }

    function moveStars() {
        for (i = 0; i < numStars; i++) {
            star = stars[i];
            star.z--;

            if (star.z <= 0) {
                star.z = canvas.width;
            }
        }
    }

    function drawStars() {
        var pixelX, pixelY, pixelRadius;

        // Resize to the screen
        if (canvas.width != window.innerWidth || canvas.width != window.innerWidth) {
            canvas.width = window.innerWidth;
            canvas.height = window.innerHeight;
            initializeStars();
        }
        if (warp == 0) {
            c.fillStyle = "rgba(0,10,20,1)";
            c.fillRect(0, 0, canvas.width, canvas.height);
        }
        c.fillStyle = "rgba(209, 255, 255, " + radius + ")";
        for (i = 0; i < numStars; i++) {
            star = stars[i];

            pixelX = (star.x - centerX) * (focalLength / star.z);
            pixelX += centerX;
            pixelY = (star.y - centerY) * (focalLength / star.z);
            pixelY += centerY;
            pixelRadius = 1 * (focalLength / star.z);

            c.fillRect(pixelX, pixelY, pixelRadius, pixelRadius);
            c.fillStyle = "rgba(209, 255, 255, " + star.o + ")";
            //c.fill();
        }
    }

    // document.getElementById('warp').addEventListener("click", function(e) {
    //     window.c.beginPath();
    //     window.c.clearRect(0, 0, window.canvas.width, window.canvas.height);
    //     window.warp = warp ? 0 : 1;
    //     executeFrame();
    // });

    executeFrame();

}());